Many electronic devices or systems, such as computers, tablets, and cellular phones, include components (e.g., integrated circuit chips) located on a circuit board. The components may communicate with each other using signals that can carry information (e.g., data). The signals are usually transmitted on conductive lines, such as metal-based traces, on the circuit board. Each of the signals may be organized into symbols. Each symbol is a portion of the signal within a fixed period of time.
In the pulse-amplitude modulation (PAM) technique, each symbol can be used to transmit one bit or multiple bits of information. In this technique, the signal is modulated at different amplitudes based on the values of the bits associated with the symbols. For example, in binary PAM (2-PAM) signaling, each symbol can have either one of two possible amplitude values, depending on the value (e.g., either binary 0 or 1) of the bit associated with that symbol. In other M-ary PAM (e.g., 4-PAM, 8-PAM, etc.) signaling, each symbol can have either one of M amplitude values. In some situations, transmitting signals using M-ary PAM techniques may be more favorable than some other techniques. However, in some systems, using an M-ary PAM-based technique may increase device area, power, and circuit complexity.